Bone marrow transplantation (BMT) is now widely accepted as an effective treatment for malignant and nonmalignant hematologic diseases. However, graft-versus-host disease (GVHD) is a lethal complication of allogeneic BMT. GVHD is a condition that can occur after an allogeneic transplant. In GVHD, the immune cells in the donated bone marrow attacks the recipient's tissue and organs as foreign invaders. Treating GVHD relies on the general suppression of the immune system, but this treatment leads to severe side effects like tumor reoccurrence or opportunistic infection.